Process for producing resin treated cotton batting products wherein the density of portions of the product can be varied to meet end use requirements

ABSTRACT

Variations in density, flame retardancy, resiliency, dimensional stability, coherence, integrity, and moldability are imparted to fibrous cellulosic batting upon treatment wherein the batting is impregnated with aqueous mixtures containing certain combinations of thermoplastic and thermosetting resins selected for their compatibility with each other and with such additives as urea phosphate complexes, borated urea-formaldehyde, diammonium phosphate, or boron containing organic or inorganic salts, by changes in the relative ratio of thermoplastic to thermosetting resin components.

United States Patent Knoeptler et al.

[ Feb. 29, 1972 [54] PROCESS FOR PRODUCING RESIN TREATED COTTON BATTING PRODUCTS WHEREIN THE DENSITY OF PORTIONS OF THE PRODUCT CAN BE VARIED TO MEET END USE REQUIREMENTS [72] lnventors: Nestor B. Knoepller, New Orleans; Paul A.

Koenig, Kenner, both of La.

[73] Assignee: The United States 01 America as represented by the Secretary of Agriculture [22] Filed: Oct. 10, 1969 [21] Appl.No.: 865,323

Related US. Application Data [63] Continuation-impart of Ser. No. 728,162, May 10,

1968, abandoned.

[52] U.S.Cl ....l56/62.8, 156/369, 161/166 [51] Int. Cl ..B32b17/05 [58] Field ofSearch ..l56/62.2, 62.8,180-181, 156/370-1377; 161/59, 62.6, 403, 159-166 [56] References Cited UNITED STATES PATENTS 2,372,433 3/1945 Koon ..161/159 3,246,064 4/ 1966 Moor et al. ...1$6/62.2 3,323,944 6/1967 Senez ....1 17/136 3,350,486 10/1967 Knoepfler et al. ..264/112 Primary ExaminerBenjamin A. Borchelt- Assistant Examiner-H. Tudor Attorney-41. Hoffman and W. Bier [57] ABSTRACT Variations in density, flame retardancy, resiliency, dimensional stability, coherence, integrity, and moldability are imparted to fibrous cellulosic batting upon treatment wherein the batting is impregnated with aqueous mixtures containing certain combinations of thermoplastic and thermosetting resins selected for their compatibility with each other and with such additives as urea phosphate complexes, borated urea-formaldehyde, diammonium phosphate, or boron containing organic or inorganic salts, by changes in the relative ratio of thermoplastic to thermosetting resin components.

1 Claims, 3 Drawing Figures PATENTEDFEB29 1912 SHEET 1 [IF 3 v INVENTORS NESTOR B. KNOEPFLER PAUL A meme W gr I ATTORNEY5 PATENTEDFEBZQ m2 3,645,814

' sumanrs INVENTORS NESTOR B.KNOEPFLER PAUL A. KOENIG ATTORNEYS PROCESS FOR PRODUCING RESIN TREATED COTTON BATTING PRODUCTS WHEREIN THE DENSITY OF PORTIONS OF THE PRODUCT CAN BE VARIED TO MEET END USE REQUIREMENTS This invention relates to and Supplements the invention described and claimed in US. Pat. No. 3,181,225, which issued May 4, 1965, and in US Pat. No. 3,350,486, which issued Oct. 31, 1967, and application bearing Ser. No. 50,306 filed June 26, 1970, which is acontinuation-in-part of Ser. No. 728,162, filed May 10, 1968, now abandoned.

A nonexclusive, irrevocable, royalty-free license in the invention herein described throughoutthe world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to fibrous cellulosicbatts that have a variety of preselected densities in sequence from top to bottom, and a method of producing such batts. More particularly this invention relates to fibrous cellulosic batts with improved flame retardancy, dimensional stability, coherence, integrity, resilience, moldability that readily lends itself to useful application to cushioning applications such as furniture, mattresses, and automobile seating, and to a method of producing said batt by means of a number of aqueous single mixture chemical treatments, thus improving the state of the art.

For example, in the manufacture of furniture, mattresses, and automobile cushioning it is desirable to have cushioning pads of high density against springs where the function of the pad is a distribution of the load, while a lighter density is desirable immediately beneath the upholstry fabric or ticking for purposes of comfort.

The process of the aforementioned US. Pat. No. 3,181,225 involves the treatment of fibrous cellulosic batting with thermoplastic and thermosetting resins in various combination to achieve a product with resilience and dimensional stability concurrent with an improvement in tensile strength and resistance to compaction, which is not present in conventional batting. The disclosure relating to the process of the aforementioned U.S. Pat. No. 3,350,486 teaches that by properly selecting the thermosetting components and applying them to webs of cotton fibers which are moldedwhile wet, dried, and cured to produce a product that conforms to a desired shape while simultaneously exhibiting improved resilience, tensile strength, dimensional stability, and resistance to compaction in use. The invention in the aforementioned Ser. No. 728,162 differs from this prior art in that the products of the known art, including the products of these patents, are further enhanced in that the added characteristic of flame retardancy is imparted to the batting while retaining the good qualities imparted by the known processes.

The instant invention differs from this prior art in that the products of the known art, including the products of these patents, are further enhanced in that the added versatility of producing a batting product that has a multiplicity of densities within the same structure is now possible, while the beneficial properties such as resilience, dimensional stability, integrity, coherence, tensile strength, flame retardancy imparted by the known process are retained and enhanced.

The main object of the instant invention is to provide a method of fabricating a multidensity batting by a combination of chemical and mechanical means wherein any selected density can be located in any chosen segment of the unit structure in the finished batting.

The second object'of the instant invention is toprovide a series of formulations and the conditions for their use in a process for the manufacture of a fibrous cellulosic batt which will result in a product that demonstrates difi'ering degrees of resilience, coherence, tensile strength, and resistance to compaction in use, by virtue of the fact that different portions of the said product will have different densities which can be selected to meet specific end use requirements.

The third object of the instant invention is to provide formulations for use in a process for the manufacture of a fibrous cellulosic batt with-an ability to resist damage by fire, said imtogether even though the treated materialmay be severely charred.

This invention is a product of investigative effort to combat the increasing competition to cotton material by the recent advances of natural. and synthetic foamed products, and to comply with theevident intent of the Congress of the United States of America to render cushioning materials used in places of public accommodatiomat home, and in automobiles safer in every possible respect.

The application of the chemical substances is done, generally, through a single or a plurality of nozzles, whichwet the web as it moves past a fine spray controlled as to avoid extremes in wetting the web, and at the same time to assure optimum droplet size that results in uniform deposition of the chemicals on the web.

The chemicals employed are applied in formulations consisting of both thermoplastic and thermosetting resin species either in combination or alone. The resilience and dimen-ysional stability and density characteristics of the products de'-- pend upon the proper selection of the thermosetting resin and the film-forming thermoplastic resin because their functions must of necessity be complimentary. The thermosetting resins of choice must be capable of being cross-linked with the cellulose to chemically enhance the resilience characteristics of the fibers, while the thermoplastic resin must be of a film-forming type whose physical characteristics such as bending moment,

elongation, and strength must closely approximate that of cotton since the function of the thermoplast is to bind the fibers together at points of contact to contribute to the tensile strength, dimensional stability, and density of the products.

A most important feature of the instant invention is the variation of the ratio of thermoplastic to thermosetting resin within the treating formulations and the control of the amount of treating formulations that is applied to the in-process fibers, both from a weight standpoint, and from the standpoint of uniformity of distribution, so that an effective and efficient process of economic value is achieved. 7

Also of importance is the proper selection of the thermoplastic and thermosetting component for compatibility with each other,.as well as with additives for flame retardancy so that the basic function of. each of these as described immediately above are not adverselyaffected, while advantage is taken of the more specific efiect of each upon the density and other physical characteristics of the products.

The advantages and objectives will be more apparent and a better understanding of each step can be gained upon studying the schematic drawings. 7

FIG. I isa top schematic view of the processing sequence for the production of multidensitybatting. The gametting increment of processing has been omitted to simplify the drawmg.

FIG. 2 -is an elevation schematic view showing the same .equipment as in FIG. 1, which mainly consists of conventional 'blend of 60 percent first cut linters and 40 percent of various grades of textile wastes. This particular blend is a-mere illustration. ln'actual practice these percentages can be varied to suit either the availability of the materials or the preference for other reasons. The figures shown are not considered critical for the process of the instant invention.

The feed material, above mentioned as a bland, is passed through suitable commercially available garnetting units to be formed into a web or layer of fibers. FIGS. 1 and 2 show three layers of fiber webs 1, 2, and 3 being processed by three lappers. In practice the number of lappers that could be made to do this processing can be any number, and only the quantity of available space should be considered as a limiting factor. As fiber webs l, 2, and 3 are deposited on the moving surface of conveyor belt 4 chemical formulations A, B, and C are applied to the descending webs just before the webs are released onto a conveyor belt, and each of the chemical formulations can be of a specific ratio of components different to the other. The storage tanks 5, contain these chemical formulations which are fed to the spray nozzles 7 through flexible tubing 6. Generally the spray nozzles can be about seven, and can be placed on either or both sides of the lapper structure, there being varying philosophies applicable to efficient and uniform distribution of the chemicals on the web.

In the examples of batting prepared specifically to illustrate the material produced by process of the instant invention the optimum web add-on was made to vary from 50 percent to 150 percent. The particular add-ons depended on the properties desired in the finished product. This particular range is most suitable.

Investigation of the total weight solids that might be useful in the instant invention has led to the values of about from 1 percent to 35 percent'total solids by weight as suitable spray mixtures. The total solids content selected depends many times on the resin to latex ratio desired, the viscosity or other nature of the reagents selected, and the properties desired in the finished batt.

The chemical formulations or mixtures in storage tanks may vary in that formulation A is specific for imparting to the finished batt a density of about 2.7, while formulation B is specific for imparting a rigidity to the finished batt with a density of about 6.2. On the other hand, a very fluffy surface with a great deal of flame retardancy might be needed on the opposite side of the same batting unit structure. In that case the formulation C should contain the chemical constituents which would impart to that increment of the finished batt a density of about 1.4 and a suitable quantity of flame retardants. The relative density, the web add-on, the thermoplasticity, the pliability, the rigidity, the flame retardancy, and many other qualities can be varied from one increment to the other within a single structural entity by varying the chemical ingredients in the selected formulations. Furthermore, each of the increments which are portions of the finished batt of the instant invention are continuous with the other. There is a coherence within the structural entity which makes the entire structure hold together no matter what the density or other qualities are imparted to the different areas. 1

Versatility in the selection of the location of the most dense, the least dense, and any or all intermediate densities is achieved simply by changing the chemical formulation for successive spray assemblies. Thus, the web output of crosslapper I canbe sprayed with a formulation which yields a preselected density of lapped webs 8, and then the output of cross lapper 2 can be sprayed with a formulation which yields a different preselected density of lapped webs 9. These webs are lapped continuously on the lapped webs 8, thereby at this point constituting potentially a two-density mass of chemically sprayed fibers. As the mass moves to the right in both FIGS. 1 and 2 a third layer of webs 10 is lapped on top of lapped webs 8 and 9. At this point potentially there is a three-density mass of chemically sprayed fibers. As was explained earlier in the specification, this technique can be employed theoretically uncndingly to produce a finished batting with any number of densities, and any variety of other qualities controllable by the chemical formulations and sequence of application.

A drying and curing oven 11 receives the chemically sprayed and lapped webs conveyed to it by the conveyor belt 4. The removal of solvents and the reaction between cellulose and other chemical ingredients generally takes place in the time it takes to traverse the length of the oven. The dried and cured batting 12 with multiple density is received by a takeup roll 13, which must be removed and replaced periodically to maintain the continuity of the process and ease in operation.

The formed batting is constricted in such a manner as to maintain a specific height during drying and curing; or dried and cured without restraint depending on the desired physical properties. Since a structure consisting of cellulosic fibers which have been formed into batts tends to expand in volume when subjected to heat or hot air circulation, this invention takes advantage of this inherent characteristic in order to achieve different densities in the finished product. The density of an individual segment of the product therefore can be varied by either varying the weight of the individual webs, the number of webs, or segments used in the batt, or by changing the ratio of thermoplastic to thermosetting resin in the treating formulation, or by selecting thermoplastic resins having differing abilities to form films or different film physical properties.

Drying temperatures up to 345 F. can be used depending on whether drying will be carried out simultaneously with curing or as a separate unit operation to be followed by curing. In the latter instance drying temperatures up to 200 F. would be adequate for drying if followed by temperatures of up to 345 F. for curing. Suitable temperatures within this range can be selected depending upon the requirements of the chemicals employed. Evidence exists that the degree of expansion obtained in the finished product depends upon a relationship between the time of drying and the temperature employed. In general longer times at lower temperatures will result in a more expanded structure in the finished product.

Upon the completion of the drying and curing step or steps the product retains its preselected height, width, and length. Furthermore, the product is one having improved resilience, a resistance to deformation from compressive loading much greater than untreated cotton batting, and demonstrates a cohesive structure and resistance to compaction in use. In addition the product made as a result of the practice of this invention has significantly greater tearing and tensile strength, up to 20 times as great as untreated cotton batting. The performance of the improved product can be demonstrated both at highand low-relative humidities.

FIG. 3 depicts a type of automobile seat known as a bucket seat which is popular in today's automobiles. The base portion 14 and the back portion 15 can require different cushioning characteristics. Generally, these do not have an identical construction. A cutaway view 16 along the edge of the base portion 14 is shown in the exploded view to illustrate an application of the instant invention. The exploded view shows segments 8, 9, and 10 as being of approximately the same thickness. This is not a prerequisite for these layers can be any chosen thickness. This particular illustration represents a batting having the greatest density segment 8 lowermost and ranging in density about from 3.5 to 4.5 pounds per cubic foot.

This layer can rest directly on the springs and requires no base pad. The middle segment is a medium density segment 9 having a density of about from 2.5 to 3.5 pounds/cu. ft. The upperrnost segment 10 functions as a topper pad and has a density of about from 1.5 to 2.5 pounds/cu. ftfThus, the product which is a portion of the instant invention, a batting with multiple density segments within a singular structural unit in any configuration, enables one to use this single cushioning product where several separate layers had been required prior to our invention in order to obtain all of the physical requirements.

Treatment using a number of single media formulations has been accomplished by research, which included the search for compatible systems each of which can contain the resin, the latex, the catalyst, the thickening agent, the flame retardant, the dyes, and the solvents, which go into the spray application in a single solution or suspension or both.

Pretreatments of the raw stock feed, such as mercerization, scouring, and wet processing with chemicals such as formaldehyde, significantly enhance the properties of the finished product. Likewise the flame retardant can be applied as a pretreatment for the cotton raw stock followed by drying. In this case the flame retardant could be eliminated from the subsequent formulation.

The many facets of this process, and their proper application by adjusting to the most suitable variables make it evident that there are many advantages to be gained in the practice of this invention. The following specific examples refer to materials actually produced on an experimental basis, and are in no way to be construed as specific limits to the flexibility of the system.

The batts produced by the use of this invention are dimensionally stable and resilient, and demonstrate a marked ability to reproduce contours of the material used to restrain them during drying and curing.

Since the resins found to contribute the enhanced properties described herein for cotton fibers are known to chemically react with the cellulose of the cotton fibers, such resins can be expected to react equally well with synthetic cellulosic fibers such as rayon. For this reason the process described herein for the manufacture of a fibrous cotton batt is equally applicable to the fibrous cellulosics or blends of these materials with cotton.

Such resins as the urea formaldehydes, tris(l-aziridinyl) phosphine oxide, melamines, triazines and other will react equally well with wool as with cotton. For this reason the procex described herein for the manufacture of a fibrous cotton batt is equally applicable to wool or blends of wool and cotton.

Because textile wastes normally used in the production of cotton batting are derived from diverse sources, on occasion these wastes may contain varying nominal amounts of synthetic fibers such as polyesters or acrylics, polyethers or others either by chance or design. The presence of these synthetic fibers would not preclude the use of the waste in the practice of this invention.

In general, according to the instant invention, the method for producing a fibrous cotton batt with improved dimensional stability, coherence, moldability, and resilience that is flame retardant, comprises the following operations carried out in sequence:

a. forming webs of opened cellulosic fibers of the group consisting of cotton fibers and chemically modified cellulosic fibers,

b. treating the webs with an aqueous 5 to 40 percent solids formulation consisting of about to 88 percent of a thermoplastic substance, about from 68 to 12 percent of a thermosetting polymer-forming substance, and about from 2 to 20 percent of an agent capable of imparting flame-retardancy to cellulosic materials, respectively, plus an appropriate catalyst when necessary, the ratio of thermoplast to thermoset to fineretardant depending upon the desired density of the product being produced, to obtain a wet-pickup of about from 50 to 150 percent, which treatment yields a product with a chemical add-on of about from 5 to 25 percent by weight of the cellulose component,

c. collecting and condensing the treated webs to form a laminated batt of layered, treated webs, and

d. curing the laminated batt of layered treated webs under compression less than the ultimate use compression of the finished batt. v u g In reference to step (b), the preferred quantities of thermoplastic substance:thermosetting polymer-forming substancezflame retardant is 46:46:8.

The figures and disclosures thus far discussed are meant as illustrations of the invention and should not be construed as limiting the invention in any way whatever.

EXAMPLES Fifteen different chemical formulations were prepared having different ratios of ingredients, varying in percent of total solids, and varying in the specific type of ingredients in order to impart a variety of chemical and/or physical properties to cellulosic batts.

The series of experiments was designed so as to yield five finished batts having within each of these units of structure more than one density. The chemical ingredients chosen were chosen from various resins, various latex substances, and two different flame retardants. The finished batts were identified as Samples V, W, X, Y, and Z, each having at least two density increments. Each of the different density increments was identifiable visually by a dye included in each formulation so that the finished product would show the different increments of density as a different color. For tabulation purposes the increments-were referred to as Sections A, B, C, and D.

The method of application of the selected formulations was unique but simple. Ordinarily three or more gametts, feed webs onto a conveyor belt to yield an impregnated battor a nonimpregnated batt and where chemicals are used, the same formulation is sprayed on the webs from all garnetts. The instant invention differs in that each of the lappers we sprayed a formulation which would yield a different density in the finished product. The spray damp batt thus formed varied in wet pickup from about 50 to percent. The spray damp batt was fed at the rate of about from 4 to 22 feet per minute into a drying and curing oven where it was dried at about to 220 F. and cured at about 300 to 350 F. The cured batts thus produced had an average dry weight pickup varying about from 5 to 25 percent, and a thickness of about from three-fourth to 1 /2 inches. The finished batts were made by choice to vary in density about from 1.5 to 3.3 pounds per cubic foot within the same structural entity. Each and every one of these factors can be controlled individually for each segment of the structural entity.

The finished batts were submitted to physical tests and evaluated for various significant qualities. The results of some of these experiments are presented in Tables I through VI, the latter being strictly for identification of codes used throughout. Other pertinent information is self-explanatory.

The examples presented here are illustrations of how the invention has been utilized and are not to be construed as limiting the invention is any manner whatever.

To summarize, the instant invention can best be described as a batt having a plurality of densities within a single structural entity, and the method of producing the said batt. The method of the invention can be described best thusly:

A method of producing a fibrous cellulosic batt possessing inherently the quality of a plurality of densities within a structural entity and in any preferred order as well as one or a plurality of physical properties selected from the group consisting of dimensional stability, coherence, moldability, resilience, and flame retardance, comprising:

a. forming webs of opened cellulosic fibers from a plurality of garnetts,

b. spray-treating the plurality of webs with a plurality of chemical formulations each of which is formulated to yield various selected density and other physical property to ultimately impart the desired density and physical property desired on the final batt; the said formulations being aqueous 5 to 40 percent resin formulations, by weight, consisting of mixtures of thermoplastic, thermosetting, and flame retardant substances plus an appropriate quantity of catalyst and buffer when necessary, the number of the said plurality being contingent upon the number of densities desired in the final batt;

c. lapping plurally the variously spray-treated webs from (b) onto the upper surface of a conveyor belt, wherein the garnetted webs are fed plurality onto a horizontally traveling conveyor belt and the uncured batt being formed upon deposition of the web spray treated with one formulation on top of the web of the adjacently lapped on ad infinitum, as the conveyor belt moves the collected and condensed spray-treated webs toward the curing oven, and

d. curing the batt prepared in (c) while under compression less than the ultimate use compression of the finished batt, to yield a batt having a plurality of preferred densities as well as one or many physical properties contingent upon the chemical formulations of step (b).

TABLE V.-FLAME RESISTANCE PERFORMANCE coco nae:

TABLE L-EFFEC'I OF FORMULATION N DENSITY iinmlilh Section Section Section Section ll A B C D IE Total solids in spray, percent; 20.0 20.0 20.0 26.0 f Solids Solids Solids Solids ratio ratio ratio ratio Resin: MMM 63.0 60.0 40. 0 27.0 Latex: PVA 27. 0 40. 0 50. (T 63. 0 Flame retardant: UP 10. 0 10. 0 10.0 10.0 Density, lbs/cu. ft 2.0 2. 3.1 3. 3

W Resin: MMM 63.0 "27.0 Latex: PVC-AC RY. 27.0 63. 0 Flame retardant UP 10. 0 10. 0 Density, lbs./.cu. ft 2.2 3.3

TABLE VI.-CODE FOR TABLES TABLE II.-EFFEC'I OF FORMULATION ON DENSITY 'Iihree Symbol Chemical composition 1 y samples AC RY Polyvinyl acrylate.

A BAP Borated amido polyphosphate. Section Section Section BUF Borated urea formaldehyde. B A B C DMDHEU. Dimethylol dihydroxy ethylene urea.

Total solids in spray, percent... S S s I?IgY. filtltyalidlanldfild h d O S 0 S 0 S earn 116 orma e y e. C. ratio ratio ratio MMM. Methylated methylol melamine.

PVA Polyvinyl acetate. X ResimMF 70.0 45.0 20.0 PV Polyvinyl chloride.

Latex: ACRY- 20.0 45.0 70.0 PVC/ACR Polyvinyl chloride/acrylate copolymer. glame retlard/an 10.0 1212! 13.2 gl gc gplyvin glictleg a chloride.

ensit bs.cu.-it-- 1. yreneu a one.

y UDAP Urea-diammonium phosphate. Y Eetsin:l2g}11)HEU g grea tolrmalktliethyde. l

a 6X: a A rea-p OS!) a a comp 6X. Latex: SBR 0.0 55.0 70.0 MUF Modified urea formaldehyde. Flame retardant: UP 10.0 10. 0 10.0 Density, lbs/cu. It 2.1 2. 3 2. 6 Z 1882383088 3313311111: 88 4838 2838 We claim Latex: ACRY 20.0 0. 0 0. 0 l. A method of producing a finished batt composed of a plu g &8 8&8 1 8:3 rality of layers of cellulosic fibers having'a multiplicity of den- Density, lbs/cu. it... 2.1 2.7 3.0 sities, contiguous with each other in preselected sites, and

structurally within a single entity, comprising: TABLE III, RESILIENCE CHARACTERISTICS a. forming a first layer of open-structure webs of cellulosic sample number v w X Y Z Control 1 fibers which have been spray-impregnated to a wetpickup within the range of about from 50 to 150 percent ggg g fg figg i 2 4 2 3 2 3 2 2 2 2 3 with a first chemical formulation specifically selected to Reeoveryirom c cii yield a layer of webs having a predetermined density 94 3 90 6 95 0 92 1 95 2 91 5 within the range of about from 1.5 to 3.3 pounds per 1 1.; 1 1- cubic foot, said first formulation comprising an aqueous Recover from a cue solution-suspension containing about from 5 to 40 per- 1oad;ng100% 88 cent by weight of mixtures composed of (I) about from 12 g: Zg-g 3kg {33-8 F g-g 35% 3-2 to 68 percent of thermosetting resins selected from the 46111111111111: 76:7 1510 711a 7510 7114 76:6 '60 group consisting of methylated methylol m n p s percent melamine formaldehyde dimethylol dihydroxy ethylene .0 .2 5. .9 1 01b [sq in 10m) 62 e0 0 63 1 6 s 56 urea, and modified urea formaldehyde, (ll) about from Composite dens ty. N A d I n A MM *W V 30 to 88 percent of thermoplastic resins selected from the TABLE IVPFLAME RESISTANCE PERFORM ANOE group conslsting of polyvinyl acetate, polyvinyl chloride- 7 65 acrylate copolymer, polyvinyl acrylate, and styrene-bu- Sample number V W Y Z Control 1 tadiene, and (Ill) about from 2 to 20 percent of flame reconditioned F, 65% tardants selected from the group consisting of urea- Rfi name 0 0 0 5 0 0 0 0 0 0 0 0 phosphate complex and borated amido polyphosphate, Mm glow "j: 1 M and wherein theweight ratio of thermosetting resin to gl uzg g lpl. 1 1; lg-g 11 M 3-8 5-; 70 thermoplastic resin to flame retardant is 46:46:8; sonkm l 1d b. forming a second layer of open-structure webs of cellu- 158 11: losic fibers which have been spray/impregnated to a wet- .88885 81888883111333: 8:8 8:8 8:8 8:8 8:8 8:8 Pickup within the same ang f a ut from so m 150 Overall char (0111.) 12.0 11.0 9.0 4.5 4.0 4.0 ercent s ecifi in Mam char (cm) M 1.0 3.5 1.5 L5 1.5 2.0 p p ed step (a), with a second chemical for mulation containing the same ingredients described in step (a), but varied therefrom by selection of proportions to yield a second layer of webs having a predetermined density within the same range of about from 1.5 to 3.3 pounds per cubic foot specified in step (a), but different from that produced by step (a), and depositing said second layer of open-structure webs on top of the first layer of webs produced by step (a) in a layered relationship;

c. forming a third layer of open-structure webs of cellulosic fibers which have been spray-impregnated to a wetpickup within the said range of about from 50 to 150 percent specified in steps (a) and (b), with a third chemical formulation containing the same ingredients described in steps (a) and (b), which ingredients may be present in the same or different selected proportions from those specified in steps (a) or (b), to yield a third layer of webs having a predetermined density within the same range of about from 1.5 to 3.3 pounds per cubic foot specified in steps (a) and (b), which density may be the same or different from either of the densities of the products produced by steps (a) or (b), and depositing this third layer of spray-impregnated webs on top of the second layer of webs produced by step (b) in a layered relationship;

d. forming as many additional layers of open-structure webs of cellulosic fibers which have been spray-impregnated to a wet-pickup within the aforesaid range of about from 50 to percent specified in the preceding steps, with a corresponding number of additional chemical formulations containing the same ingredients described in the preceding steps, which ingredients may be present in the same or different selected proportions from those specified in the preceding steps, to yield additional layers of webs having predetermined densities within the aforesaid range of about from 1.5 to 3.3 pounds per cubic foot specified in the preceding steps, which densities may be the same or different from any of the densities of the products produced in the preceding steps, and depositing these additionally produced layers of spray-impregnated webs on top of the aforesaid third layer of webs produced by step (c), in a layered relationship to produce a batt;

. drying the batt obtained from step (d), at a temperature of about from to 220 F and curing the dried batt from step (e) at a temperature of 

